TrajAD: Trajectory Anomaly Detection for Trustworthy LLM Agents

Fuente: arXiv
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Autores principales: Liu, Yibing, Zhang, Chong, Han, Zhongyi, Liu, Hansong, Wang, Yong, Yu, Yang, Wang, Xiaoyan, Yin, Yilong
Formato: Preprint
Publicado: 2026
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author Liu, Yibing
Zhang, Chong
Han, Zhongyi
Liu, Hansong
Wang, Yong
Yu, Yang
Wang, Xiaoyan
Yin, Yilong
author_facet Liu, Yibing
Zhang, Chong
Han, Zhongyi
Liu, Hansong
Wang, Yong
Yu, Yang
Wang, Xiaoyan
Yin, Yilong
contents We address the problem of runtime trajectory anomaly detection, a critical capability for enabling trustworthy LLM agents. Current safety measures predominantly focus on static input/output filtering. However, we argue that ensuring LLM agents reliability requires auditing the intermediate execution process. In this work, we formulate the task of Trajectory Anomaly Detection. The goal is not merely detection, but precise error localization. This capability is essential for enabling efficient rollback-and-retry. To achieve this, we construct TrajBench, a dataset synthesized via a perturb-and-complete strategy to cover diverse procedural anomalies. Using this benchmark, we investigate the capability of models in process supervision. We observe that general-purpose LLMs, even with zero-shot prompting, struggle to identify and localize these anomalies. This reveals that generalized capabilities do not automatically translate to process reliability. To address this, we propose TrajAD, a specialized verifier trained with fine-grained process supervision. Our approach outperforms baselines, demonstrating that specialized supervision is essential for building trustworthy agents.
format Preprint
id arxiv_https___arxiv_org_abs_2602_06443
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle TrajAD: Trajectory Anomaly Detection for Trustworthy LLM Agents
Liu, Yibing
Zhang, Chong
Han, Zhongyi
Liu, Hansong
Wang, Yong
Yu, Yang
Wang, Xiaoyan
Yin, Yilong
Cryptography and Security
Artificial Intelligence
We address the problem of runtime trajectory anomaly detection, a critical capability for enabling trustworthy LLM agents. Current safety measures predominantly focus on static input/output filtering. However, we argue that ensuring LLM agents reliability requires auditing the intermediate execution process. In this work, we formulate the task of Trajectory Anomaly Detection. The goal is not merely detection, but precise error localization. This capability is essential for enabling efficient rollback-and-retry. To achieve this, we construct TrajBench, a dataset synthesized via a perturb-and-complete strategy to cover diverse procedural anomalies. Using this benchmark, we investigate the capability of models in process supervision. We observe that general-purpose LLMs, even with zero-shot prompting, struggle to identify and localize these anomalies. This reveals that generalized capabilities do not automatically translate to process reliability. To address this, we propose TrajAD, a specialized verifier trained with fine-grained process supervision. Our approach outperforms baselines, demonstrating that specialized supervision is essential for building trustworthy agents.
title TrajAD: Trajectory Anomaly Detection for Trustworthy LLM Agents
topic Cryptography and Security
Artificial Intelligence
url https://arxiv.org/abs/2602.06443